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King and Jukes begin with a
polemically-worded introduction, in which they proclaim that recent
developments in molecular biology have made it both possible and
necessary to reexamine many of the assumptions of Darwinism. Contrary
to what "classical evolutionary biologists" like G.G. Simpson believe,
they suggest that evolution at the molecular level may be governed by a
mechanism completely different from natural selection. Indeed, they
argue that most mutations that become fixed in the genome must be
selectively neutral, since Darwinian evolution at the rate of one amino
acid substitution every 2 years (or even every 50 years) would be more
costly than any species could afford. While they agree with Kimura
(1968) on this point, they find fault with his methodology on many
points, including: his failure to take into account the lethality of
most mutations and his assumption that most mammalian DNA consists of
structural genes. Indeed, King and Jukes argue that only about 5-10% of
nucleotide substitutions are neutral, occurring primarily in regions
that are not involved in protein function. King and Jukes support their
conclusion with a litany of data from comparisons of protein and DNA
sequences in a wide variety of species.

This page was written by Michael Dietrich and Jay
Aronson. It was last updated on May 15, 2004.